Transformer with winding sections connected in series or parallel



Aug. 11, 1964 3,144,628

L. RABINS TRANSFORME ITH WINDING SECTIONS CONNECTED IES OR PARAL Fi April 10, l

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United States Patent 3,144.,628 TRANSFURWR WITH WINDING SECTIONS CONNECTED IN SERIES 0R PARALLEL Leonard Rabins, Pittsfield, Mass, assignor to General Electric Company, a corporation of New York Filed Apr. 10, 1961, Ser. No. 102,035 4 Claims. (Cl. 336-182) This invention relates to electrical transformers, and more in particular to transformers having windings that can be connected in more than one way for use with different voltages having three-to-one ratios.

It is common practice to arrange a transformer winding so that the transformer can be employed to produce different output voltages. It is also common to arrange transformer windings so that the transformer can be employed to produce a given voltage output for different input voltages. This has been accomplished in the past by dividing the windings into several groups of turns that can be connected in various series or parallel arrangements that produce the desired voltage. In designing variable input or variable output power transformers, problems arise when portions of the windings are connected in different arrangements because some portions will carry more current than others. This can result in portions of the winding overheating, additional load losses, and different winding reactances for the various connection arrangements. Consequently, in any commercialy usable power transformer the winding arrangement must be such that substantially equal current division will occur among the various winding portions and the winding reactance must be balanced.

In the so-called disc type winding construction various arrangements meeting the above requirements are wellknown. However, in the so-called layer winding arrangements serious problems have been encountered. For example, in one known prior art layer winding arrangement, the winding was divided into three concentric, radially-spaced axial layers of turns. Each layer of turns was divided into three axially spaced sections. For a series winding arrangement, the sections in each layer were connected in series and then each layer was connected in series with the next layer. For the parallel winding arrangement each section in each layer was connected to radially and axially spaced sections of other layers by cross-over leads at the interior portion of the winding, and the outer ends of each layer were connected in parallel. Although this winding arrangement solves the problems of unequal current and reactance distributions, the cross-overs in the interior of the winding increased the radial build of the winding which resulted in an undesirable increase in the size, weight, and cost of the transformer.

Accordingly, it is an object of my invention to provide an improved transformer construction that solves the problems mentioned above.

Another object of my invention is to provide an improved transformer winding in which the leads for changing from series to parallel connections emerge from the axial outer ends of the winding.

A further object of my invention is to provide a transformer for operation at variable input or variable output voltages that it lighter, more compact, and more economical by virtue of improved winding construction.

Another object of my invention is to provide a transformer having a layer winding that has groups of turns connectable in either series or parallel relationships in which none of the changeable connections between the groups of turns are at the interior of the winding.

Briefly stated, according to one aspect of my invention, a transformer capable of operating at or producing different voltages with the ratio of 3:1 may be provided with 3,144,628 Patented Aug. 11, 1964 a unitary winding sub-divided into radially concentric layers of turns that are adapted to be connected in predetermined series and parallel relationships. The radially innermost winding layer has approximately of the total number of turns in the winding and the radially outermost layer has approximately 3 the tot-a1 number of turns in the winding. Two central layers are provided between the innermost and outermost layers. Each central layer is split into upper and lower sections, each of which has approximately one-sixth of the total number of turns in the winding. The upper sections of the central layers are substantially axially coextensive and may be permanently connected in series. The lower sections of the central layers are also substantially axially coextensive, and also may be permanently connected in series.

Other objects and advantages of my invention will become apparent from the specification, drawing, and claims which follow, and the scope of the invention will be pointed out in the claims.

In the drawing:

FIGURE 1 is a top plane schematic view showing the relative positions of the winding layers in a transformer according to my invention.

FIGURE 2 is a circuit diagram showing the series winding connections for the transformer of FIGURE 1.

FIGURE 3 is a circuit diagram corresponding to FIG URE 2, showing the parallel winding connection.

FIGURE 4 is a schematic plan view taken in the direction of the arrows 4. in FIGURE 3 indicating the direction in which various layers are wound.

FIGURE 5 is a schematic plan view taken in the direction of the arrows 5 in FIGURE 3 indicating the direction in which other layers are wound.

The invention will now be explained in reference to the drawing. FIGURE 1 shows a unitary winding 9 for a transformer in which four radially concentric substantially cylindrical winding layers 11, 12, 13, and 14 surround and extend axially along a leg 10 of a magnetic core. While the winding 9 is made up of a plurality of discrete coils (i.e. winding layers or sections) each having two terminals, it is unitary in the sense that in operation the separate coils are electrically connected together in series or parallel or some combination of series or parallel so that together they constitute one single winding with respect to the main input or output terminals of the transformer. FIGURES 2 and 3 show how the winding layers may be interconnected to provide a transformer with an output that can be varied in a 3 :1 ratio or that can have a constant output when used with input voltages that vary in a 3:1 ratio. When the input voltages vary in a 3:1 ratio and a constant output is desired, the winding 9 will be the primary winding of the transformer. When the input voltage is constant and output voltages that vary in a 3: 1 ratio are desired, the winding 9 will be the secondary winding of the transformer. The following description of how the various groups of turns are connected in series or in parallel in applicable whether the winding 9 is primary or secondary.

A radially innermost winding layer 11 extends continuously axially for substantially the entire length of the core leg 14). A radially outermost winding layer 14 also extends continuously axially for substantially the entire length of the leg 10. A first split central winding layer 12 is divided into an upper section 15 and a lower section 16. A second split central winding layer 13 is divided into an upper section 17 and a lower section 18.

To form a series connection between the various winding layers and sections, an axially outer end of the innermost layer 11 is connected to the coresponding axially outer end of the section 16 by a lead 20. The axially inner end of the section 16 is connected by a lead 21 to the axially interior end of the section 18. The axially outer end of section 18 is connected by a lead 22 to the axially outer end of the section 15. The axially inner end of the section is connected by lead 23 to the axially inner end of the section 17. The axially outer end of the section 17 is connected by a lead 24 to the end of the opposite radially outermost end of the section 14. If the winding 9 is one winding of a three-phase transformer, a Y connection can be obtained by connecting the remaining end of the layer 14 to line by a lead 25, and by connecting the remaining end of the innermost layer 11 to ground at 26.

To obtain the corresponding parallel connections for a Y connected winding, the following connection arrangement should be employed. An axially outer end of the innermost layer 11 is connected by a lead 31 to the corresponding outer end of the outermost layer 14-. The opposite end of the layer 11 is connected by a lead 31 to the ground point 26, and the corresponding end of the layer 14 is connected by a lead 32 to the line terminal lead 25. The radially outermost end of the section 16 is connected by a lead 33 to the ground point 26, and the innermost end of the section 16 is still connected by the lead 21 to the innermost end of the section 18. The radially outermost end of the section 13 is connected by a lead 34 to the line terminal 25. The radially outermost end of the section 15 is connected by a lead 35 to the ground point 26, and the innermost end of the section 15 is still connected by the lead 23 to the innermost end of section 17. The radially outermost end of the section 17 is connected by a lead 36 to the line terminal 25.

From the above-described arrangements, it is apparent that the interior leads 21 and 23 can be permanent con nections because the inner most ends of the windings 15, 16, 17, and 18 are connected in identically the same manner in both the series and parallel arrangements. It is also apparent that the only leads that are changed in converting from the series to the parallel connections are those at the axially outer ends of the winding. This eliminates changeable internal cross-overs at the interior of the winding that increased the radial build of prior art layer windings. It is thus apparent that my winding arrangement results in a transformer of smaller radial build, with a consequent reduction in the size, weight and cost of apparatus.

In order to obtain proper current and reactance distribution among the winding layers and sections in both the series and parallel connection arrangements, the number of turns in each winding layer and section should conform to the following requirements. The radially innermost layer 11 should have substantially one-fourth of the total number of turns in the winding 9. The radially outermost layer 14 should have substantially A of the turns in the winding 9. The combined number of turns in the layers 11 and 14 should be /3 of the total turns in the winding 9. The central layers 12 and 13 should each have /3 of the total number of turns of the Winding wtih each of the sections 15, 16, 17, and 18 having /6 of the total number of turns in the winding 9. Referring again to FIGURE 3, it can be seen when the winding layers and sections are connected in the manner described and each has the number of turns specified above, three parallel connected groups of turns will result. One group will consist of the layers 11 and 14, another group will consist of the sections 16 and 18, and the remaining group will consist of the sections 15 and 17. Thus, each group of turns will have /a of the turns in the winding.

When the number of turns employed and the radial location of the turns conform to the above-described arrangement, the current and reactance distribution in the winding 9 will be balanced in both series and parallel connections. Those skilled in the art will realize that the precise number of turns will vary somewhat because of variations in the properties of the materials employed.

and variations in the shape and location of the turns. Therefore, it is intended that the figures given above be taken as theoretically optimum figures with the understanding that slight variations would occur in actual commercial apparatus.

The various layers and sections of the winding 9 should be wound in certain relative directions in order for the induced voltages to add in the proper manner. The winding directions that achieve the desired results are indicated schematically in FIGURES 4 and 5, wherein the direction of the arrowheads on the winding layers indicate the relative direction, either clockwise or counter-clockwise, in which each layer or section should be wound around the core 1%. As indicated in FIGURE 4, when the layer 11 is wound in the clockwise direction, the section 15 should also be wound in the clockwise direction, but the section 17 and layer 14 should be wound in the counterclockwise direction. Similarly, FIGURE 5 shows that when the layer 11 is wound in. the clockwise direction, the section 16 should be Wound in the counterclockwise direction, the section 18 wound in the clockwise direction.

The above-described winding arrangement has been successfully employed for the low voltage winding of a three-phase power transformer in which it was desired that the transformer be adapted to produce one output voltage that was three times another output voltage. The transformer windings were Y-connected. When the low voltage winding was connected in the series arrangement of FIGURE 2, the output of the transformer was 69,000 volts, and when the winding was connected in the parallel arrangement in the FIGURE 3, the output of the transformer was 23,000 volts.

It has been shown that by practicing my invention a transformer can be provided with a low voltage layer winding that enables the transformer to produce one output voltage that is three times another output voltage when the input voltage is constant. By employing my layer winding arrangement for the high voltage winding, of a transformer, a constant output voltage can be obtained for an input voltage that is three times as great as another input voltage. These results are accomplished without the defects of previous layer winding arrangements that resulted in increased radial build and consequent greater weight, cost, and size of the apparatus. My invention accomplishes the improved results by employing the particular connection scheme described above so that all of the leads that must be changed when changing from series to parallel connections emerge from the axially outer ends of the winding.

It will be understood, of course, that while the forms of the invention herein shown and described constitute preferred embodiments of the invention, it is not intended herein to illustrate all of the equivalent forms or ramifications thereof. It will also be understood that the words used are words of description rather than of limitation, and that various changes may be made without departing from the spirit or scope of the invention herein disclosed. For example, terms such as upper and lower or clockwise and counterclockwise are intended to be relative, it being obvious that they cover variations such as orienting the core leg 10 horizontally rather vertically. It is aimed in the appended claims to cover all such changes as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a transformer, a unitary winding subdivided into four radially-concentric, axially-extending layers of turns comprising, a radially innermost layer having approximately one-fourth of the turns. in said winding, a radially outermost layer having approximately one-twelth of the turns, a first split central layer having upper and lower sections each of which has approximately onesixth of the turns, and a second split central layer having upper and lower sections each of which has approximately one-sixth of the turns, the upper sections of said first and second central layers being substantially axially coextensive and connected in series, and the lower sections of said first and second central layers being substantially axially coextensive and connected in series, said winding having a dual voltage rating of three to one ratio while equally using all of its turns, the higher voltage corresponding to a series connection of the radially innermost and outermost layers with the serially connected upper sections and the serially connected lower sections of the two central layers, the lower voltage corresponding to a three branch parallel connection in which one branch is the radially innermost and outermost layers connected in series, and the other two branches are the serially connected upper sections and the serially connected lower sections respectively of the two central layers, said three branch parallel connection being characterized by equal currents in each of its three branches.

2. A transformer having a unitary winding capable of operating at different voltages having a three-to-one ratio, a core having a winding leg, said winding comprising four radially-concentric axially extending layers of turns circumscribing said core leg, the radially innermost layer having approximately one-fourth of the turns in said winding, a radially outermost layer having approximately one-twelfth of the turns, a first split central layer having upper and lower sections each of which has approximately one-sixth of the turns, and a second split central layer having upper and lower sections each of which has approximately one-sixth of the turns, the upper sections of said first and second central layers being substantially axially coextensive and permanently connected in series, and the lower sections of said first and second central layers being substantially axially coextensive and permanently connected in series, said winding when operating at the higher of its two voltages having its two sets of permanently series connected sections connected in series with each other electrically between and in series with the innermost and outermost layers, and when operating at the lower of its two voltages having its two sets of permanently series connected sections connected in parallel with each other and in parallel with the innermost and outermost layers with said innermost and outermost layers connected in series with each other.

3. A transformer having a unitary winding having turns connected in predetermined series and parallel relationships, a core having a winding leg, said winding comprising a plurality of radially-concentric, axially extending layers of turns circumscribing said core leg, the radially innermost layer having approximately one-fourth of the turns in said winding, a radially outermost layer having approximately one-twelfth of the turns, a first split central layer having upper and lower sections each of which has approximately one-sixth of the turns, and a second split central layer having upper and lower sections each of which has approximately one-sixth of the turns, the upper sections of said first and second central layers being substantially axially coextensive and permanently connected in series, the lower sections of said first and second central layers being substantially axially coextensive and permanently connected in series, and a three branch parallel connection in which one branch is the radially innermost and outermost layers connected in series, and the other two branches are the serially connected upper sections and the serially connected lower sections respectively of the two central layers, whereby substantially equal current flows in each branch of said three branch parallel connection.

4. In a transformer for voltages having a three-toone ratio, a core having a winding leg, a unitary winding subdivided into radially-concentric axially extending layers of turns circumscribing said leg, said layers being adapted to be connected in predetermined series and parallel relationships, the radially innermost layer having approximately one-fourth of the turns in said winding, a radially outermost layer having approximately one-twelfth of the turns, a first split central layer having upper and lower sections each of which has approximately one-sixth of the turns, and a second split central layer having upper and lower sections each of which has approximately one-sixth of the turns, said first split central layer being circumscribed by said second split central layer, the upper sections of said first and second central layers being substantially axially coextensive and permanently connected in series, the lower sections of said first and second central layers being substantially axially coextensive and permanently connected in series, said innermost layer being wound in a given direction (i.e. either clockwise or counterclockwise) around said leg, said outermost layer being wound in the direction opposite said given direction, the upper section of said first split central layer being wound in said given direction, the lower section of said first split central layer being wound in said opposite direction, the upper section of said second split central layer being wound in said opposite direction, and the lower section of said second split central layer being wound in said given direction, said winding having a dual voltage rating of three to one ratio while equally using all of its turns; the higher voltage corresponding to a series connection of the radially innermost and outermost layers with the serially connected lower sections of the two central layers, the lower voltage corresponding to a three branch parallel connection in which one branch is the radially innermost and outermost layers connected in series, and the other two branches are the serially connected upper sections and the serially connected lower sections respectively of the two central layers, whereby substantially equal current flows in each branch of said three branch parallel connection.

References Cited in the file of this patent UNITED STATES PATENTS 1,740,093 Horelick Dec. 17, 1929 1,949,809 Pedrazzo Mar. 6, 1934 2,470,598 Biebesheimer May 17, 1949 2,987,684 Doucette June 6, 1961 FOREIGN PATENTS 76,083 Norway Mar. 16, 1944 

1. IN A TRANSFORMER, A UNITARY WINDING SUBDIVIDED INTO FOUR RADIALLY-CONCENTRIC, AXIALLY-EXTENDING LAYERS OF TURNS COMPRISING, A RADIALLY INNERMOST LAYER HAVING APPROXIMATELY ONE-FOURTH OF THE TURNS IN SAID WINDING, A RADIALLY OUTERMOST LAYER HAVING APPROXIMATELY ONE-TWELFTH OF THE TURNS, A FIRST SPLIT CENTRAL LAYER HAVING UPPER AND LOWER SECTIONS EACH OF WHICH HAS APPROXIMATELY ONESIXTH OF THE TURNS, AND A SECOND SPLIT CENTRAL LAYER HAVING UPPER AND LOWER SECTIONS EACH OF WHICH HAS APPROXIMATELY ONE-SIXTH OF THE TURNS, THE UPPER SECTIONS OF SAID FIRST AND SECOND CENTRAL LAYERS BEING SUBSTANTIALLY AXIALLY COEXTENSIVE AND CONNECTED IN SERIES, AND THE LOWER SECTIONS OF SAID FIRST AND SECOND CENTRAL LAYERS BEING SUBSTANTIALLY AXIALLY COEXTENSIVE AND CONNECTED IN SERIES, SAID WINDING HAVING A DUAL VOLTAGE RATING OF THREE TO ONE RATIO WHILE EQUALLY USING ALL OF ITS TURNS, THE HIGHER VOLTAGE CORRESPONDING TO A SERIES CONNECTION OF THE RADIALLY INNERMOST AND OUTERMOST LAYERS WITH THE SERIALLY CONNECTED UPPER SECTIONS AND THE SERIALLY CONNECTED LOWER SECTIONS OF THE TWO CENTRAL LAYERS, THE LOWER VOLTAGE CORRESPONDING TO A THREE BRANCH PARALLEL CONNECTION IN WHICH ONE BRANCH IS THE RADIALLY INNERMOST AND OUTERMOST LAYERS CONNECTED IN SERIES, AND THE OTHER TWO BRANCHES ARE THE SERIALLY CONNECTED UPPER SECTIONS AND THE SERIALLY CONNECTED LOWER SECTIONS RESPECTIVELY OF THE TWO CENTRAL LAYERS, SAID THREE BRANCH PARALLEL CONNECTION BEING CHARACTERIZED BY EQUAL CURRENTS IN EACH OF ITS THREE BRANCHES. 